Corona discharge device



E. TIGER ETAL 3,277,298

2 Sheets-Sheet 1 E M C H MU 56% Q w F 5 Q N hu h n/ r W A i T WE E W m3 E I d WIATTORNEYS Oct. 4, 1966 CORONA DISCHARGE DEVICE Filed Oct. 5, 1964 Oct 4, E TIGE ETAL CORONA DISCHARGE DEVICE Filed Oct. 5, 1964 2 SheetsSheet 2 INVENTOR5 EM/L. 77662 ESK/NE 6. CORMAN M W Q 2 KeAm/sn/ IQFE/CK ATTORNEYS United States Patent 3,277,298 CORONA DISCHARGE DEVICE Emil Tiger, Highland Park, Erskine G. Corman, Forest Park, and Kenneth R. Reick, Downers Grove, Ill., assignors to Formfoto Manufacturing Company, Villa Park, Ill., a corporation of Illinois Filed Oct. 5, 1964, Ser. No. 401,626 20 Claims. (Cl. 250-495) This invention relates to improvements in coronadischarge devices, and more particularly to such devices utilized in applying electrostatic charge to paper for producing copies electrophotographically.

In order to apply electrostatic charge to copy paper in the production of electrophotographic copies, the paper is subjected to the corona discharge from one or more electrically charged wires adjacent to which at least a suitably treated or coated surface of the copy paper is passed just prior to exposure of the paper surface to an optically scanned suitably illuminated face of a master document to be copied.

Prior devices of this type have been deficient in one or more respects among which may be mentioned complexity of structure, time consuming and therefore costly assembly, difficulties in maintaining freedom from contact of the charged paper relative to the metal components of the device, excessive power consumption, and the like.

An important object of the present invention is to provide a new and improved simplified, highly efiicient, easily and quickly assembled corona discharge device.

Another object of' the invention is to provide a new and improved corona discharge device in which novel guide means prevent contact of the charged paper with any metal component and more particularly the metal shield or hood over the corona wires.

Still another object of the invention is to provide a new and improved corona discharge device having a novel self-sustaining synthetic plastic dielectric body structure.

Afurther object of the invention is to provide a new and improved corona discharge device affording a novel assembly of plastic body and metalhood structure.

Other objects, features and advantages of the present invention will be readily apparent from the accompanying drawings showing a preferred embodiment of the invention and in which:

FIGURE 1 is a side elevational view of a corona discharge device embodying features of the invention;

FIGURE 2 is a plan view of the paper guiding face of one of the separable sections of the device;

FIGURE 3 is an enlarged fragmental plan view of the uncovered back of one of the corona device sections;

FIGURE 4 is a fragmental inner face plan view of one of the metal hoods or shields of the device;

FIGURE 5 is an enlarged transverse sectional detail view taken substantially on the line VV of FIGURE 1;

FIGURE 6 is a fragmentary longitudinal sectional detail view taken substantially on the line YIVI of FIG- URE 2;

FIGURE 7 is a fragmentary longitudinal sectional detail view taken substantially on the line VII-VII of FIG- URE 2. I

In the illustrated embodiment of the invention separably attached, opposed, complementary sections 10 and 11 cooperate to define therebetween a passage 12 of a width sufficient to clear the widest copy sheet intended to be electrostatically charged. To this end, each of the sections 10 and 11 comprises an elongated hollow, dielectric oneiece body frame 13 provided with a flat face base panel structure 14 engageable in abutment with the like face of the companion section and provided with a recess 15 af fording with the companion section the passage 12 of the "ice desired width and depth entirely across and through the assembly, as best seen in FIGS. 1 and 5.

' In order to guide a paper sheet P in a path through the passage 12 with minimum contact and to afford full exposure of the opposite surfaces of the sheet to the corona discharge from charged wires 17 strung longitudinally within the frame body 13 of each of the sections 10 and 11, respective series of integrally connected, longitudinally spaced transversely diagonally extending strip-like paper guide spacers 18 are provided bridging across opposite spaced longitudinal side flange walls 19 on passagerecessed'edge portions of such walls. These spacer guides are made as thin as practicable in their respective planes normal to the longitudinal axis of the device so as to afford a minimum of corona obstruction while having adequate flange width along such planes. To avoid deflecting the paper sheet from a straight path through the passage 12, the spacer guides 18 are provided in two oppositely diagonal groups in each set, located each way from the longitudinal center, as best seen in FIGURE 2. By preference, the diagonal relationship of the groups of spacer guides 18 on the respective opposed body members 13 are arrangedin complementary relation so that they align with one another, mirror fashion. At their opposite ends, the spacer guides 18 are connected as ribs integrally in one piece with the respective side walls 19. For limiting paper contact, the spacer guides 18 are constructed in arched form at least on the sheet guiding edges thereof and more particularly to provide convexly arched guiding edges 20 longitudinally of the guiding and spacer strips 18, as best seen in FIGS. 1 and 5.

For holding the dielectric plastic bodies 13 in co-extensive alignment and in a strain separable united relationship, the respective face panel portions 14 thereof separatedby the passage recesses 15 are provided with complementary integral retaining pins 21 and sockets 22. The arrangement is such that adjacent to each end of each of the bodies 13-the surface 14 has one of the pins 21 and an adjacent one of the sockets 22 so that the respective pins projecting integrally from the opposing faces fit-into the sockets of the opposing face in each instance with a frictional press fit. This enables the sections 10' and 11 to be secured together in properly oriented matching assembly simply by aligning the pins 21 with the corresponding opposite sockets 22 and pressing the sections toward one another until full assembly has been effected. Separation is readily effected by grasping the sections 10 and 11 and firmly pulling the same apart.

At opposite ends of the paper passage recesses 15 of the hollow elongated body frame members 13 are provided respective inwardly facing transverse paper guide surfaces 23 on combination reinforcing web and corona wire bridge flanges 24 integrally connected to and between the longitudinal walls 19 and also integral with the respective contiguous base panel portions 14. Further reinforcement for the frame bodies 13 is afiorded by respective opposite end walls 25 integral with the base panels 14 and the adjacent ends of the longitudinal walls 19.

For supporting the corona wires 17, the bridge flanges 24 are provided with respective pairs of spaced slots 27 in their free edges generally centered between the walls 19, with the slots aligned with the corresponding slots in the opposite bridge member in each instance. The depth of the slots 27 is such as to orient the corona wires 17 in proper spaced relation to the paper passage 12. Adequate corona wire anchoring chamber areas are provided between the respective bridge flanges 24 and the end walls 25. This arrangement facilitates mounting each of the corona wires 17 as a loop with two parallel strands en- 'gaged in the respesctive longitudinally aligned slots 27.

Within one of the corona wire anchoring chamber areas both terminal end portions of the corona wire are anchored by clampingly engaging the same by means of a washer 28 against the inner face of the contiguous portion of the base wall panel 14 and about an integral tapered anchoring post 29 (FIGS. 3, and 7) onto which a securing nut 30 is self-threadingly attached.

At the opposite end of the assembly, where the corona wire is looped over the bridge flange 24, and more particularly that portion of the bridge flange defined between the corona wire slots 27, means are provided for tensioning the corona wire and for connecting the corona wire to a high potential source. For this purpose, a coiled tension spring 31 has one hooked end portion 32 engaged with the corona wire loop, and an opposite end portion hook 33 engaged with an anchoring lug 34 of an anchoring washer member 35 (FIGS. 3 and 6) engaged against the inner face of the contiguous portion of the base wall 14 about an integral tapered anchoring post 37 thereon. Retention of the washer 35 is by means of a flexibly tined press n-ut retainer 38. For connection to a high potential source, an insulated lead 39 is attached by means such as soldering 40 to the anchoring lug washer 35 and has on its opposite end means such as a jack 39a by which it is separably connectable into a high potential circuit.

Through the described arrangement, stringing of the corona wire 17 is quite readily effected by first merely looping it onto the bridge flange 24 nearest the post 37 and then engaging the two strands of the wire through the respective slots 27 of the opposite bridge flange 24 and anchoring the free terminal portions of the wire. Then, the spring 31 is hooked onto the intermediate connecting loop portion of the corona wire and onto the anchoring lug 34 whereby the corona wire is placed under light tension. By having the bridge flanges 24 as close as practicable to the sides of the paper passage 12 the length of unsupported corona wire is reduced to a minimum and therefore the possibility of wire vibration in service is also minimized.

For closing the respective longitudinal openings between the side walls opposite the guide ribs 18 and for stiffening the hollow frame bodies 13 and providing metallic shielding hoods for the corona wires 17, each of the bodies has assembled therewith a respective metal hood or cover channel 41. Each of the channels 41 is constructed to be coextensive in length and width to the associated frame body 13 inside the longitudinal walls 19 and the end walls 25, with longitudinal flanges 42 (FIGS. 2. and 4-7) lapping the inner faces of the longitudinal walls 19. This affords high transverse stability to the unit even though the elongated relatively narrow flange longitudinal walls 19 may be in the free condition thereof relatively resiliently flexible across their planes. In their planes, of course, the longitudinal walls 19 afford quite substantial resistance to bending. To enable the longitudinal cover member flanges 42 to extend the full length of the cover member 41, the bridge flanges 24 are shorter than the longitudinal walls 19 toward the open outer side of the body member, that is the side opposite to the base 14. Adjacent to each end of the cover-stiffener 41, the flanges 42 are cut out as shown at 43 to clear the respective bridge flange 24. Besides engagement with the bridge flanges 24 to maintain planar orientation of the cover member 41, each of the posts 29 and 37 extends to a length to provide a seating crown 44 in a common plane engagea'ble by the main body panel of the cover member. Frictional retention of the cover member 41 with the associated body frame 13 is through frictional sliding engagement of reduced diameter crown boss pins 45'- respectively on .the posts 29 and 37 extending through complementary apertures 47 in the adjacent end portions of the cover member 41, supplementing frictional engagement of the flanges 42 with the longitudinal walls 19, especially adjacent to the base panel portions 14, the bridge flanges 24 and the end walls 25 where complementary tolerances can be fairly maintained for frictional sliding assembly gripping of the cover flanges 42. For clearing the insulated electrical conductor or lead 39, each of the cover members 41 has in its end adjacent the lead a clearance notch 48 (FIGS. 4 and 6).

We have found that substantially greater voltage with less current input is attainable in the corona discharge by providing a longitudinal non-conductive, dielectric or insulating area, such as a strip 49, of at least slightly greater width than the spacing between the strands of the adjacent corona wire 17 and extending as a backing on the inner face of the main cover panel of the cove-r member 41. Electrically conductive areas are afforded on each side of the dielectric area. The insulating backing strip 49 may be of any suitable dielectric material, which may be directly deposited on the inner face of the cover member or may conveniently be applied in the form of a preformed strip adhesively secured to the cover member. 'It may also be a natural area of a plastic panel carrying electrically conductive metalized or applied foil or like coatings as areas along each side thereof. In practice, it has been our experience that through this arrangement about /a greater voltage is obtained by reducing the corona current input, as compared with the same assembly minus the opposing insulating strip 49, apparently due to the lower voltage drop. Efliciency in high speed charging of the paper is further enhanced by the closer location, as compared to prior arrangements, of the corona wires 17 to the surfaces of paper sheets, enabled by the arched spacer guides 18.

After each ofthe sections 10 and 11 has been completed and the sections assembled together into an operating unit as shown in FIGURE 1, the assembly is adapted to be mounted in any desired fashion in the path of paper sheets P (FIG. 5) to be electrostatically charged on travelling of the sheets through the passage 12 at relatively high speed for charging by the corona discharge of the opposed wires 17.

Material on the order of high density polyethylene may be used for the hollow, integrally molded frame bodies 13. Light weight metal such as aluminum is suitable for the cover hood channels 41.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

We claim as our invention:

1. A corona discharge device comprising,

opposed dielectric body frames defining a narrow passage gap therebetween affording a path for paper to be electrostatically charged,

corona discharge wires strung on said body frames across said passage,

and spaced apart integral dielectric spacer and paper guide ribs on said frames interposed between said wires and said path and extending generally diagonally relative to the path.

2. A corona discharge device comprising,

opposed assemblies comprising dielectric frame means defining a narrow passage gap affording a path for paper to beelectrostatically charged, means supporting corona discharge wires on opposite sides of said path,

and spaced apart spacer and guide rib flanges extending generally diagonally relative to said path and on each side of said path with their major dimension in planes extending across said wires and thin in minor dimension transversely to said planes whereby to present minimum interfering mass of the ribs to the corona discharge.

3. In a corona discharge device comprising,

opposed assemblies defining therebetween a path for paper to be electrostatically charged and having corona discharge wires extending in spaced relation across said path,

dielectric paper guide and spacer mean-s on opposite sides of said path and including spaced apart spacer rib means between the discharge wires and the path and arched toward the path.

4..A corona discharge device as defined in claim 3, wherein said spacer rib means comprise a plurality of groups on each side of said path and with the groups convergently diagonally related to one another.

5. In a corona discharge device,

a dielectric body frame comprising opposed longi- 'tudinally extending flange walls having corona discharge wire means therebetween and adapted to overlie the path of movement of the paper to be electrostatically charged,

and dielectric spacer and guide ribs connected to and between said Walls and having their major cross-sec- .ition-al dimension in planes extending across said wire means and minimum. dimension across said planes whereby to minimize obstructing the corona discharge effectiveness on paper travelling said path.

, 6. In a corona discharge device,

a molded plastic hollow body frame comprising longitudinally extending spaced wall flanges arranged to oppose. a path for paper to be electrostatically charged,

and integral paper spacer guide ribs molded at opposite ends to the respective wall flanges and adapted to oppose the paper moving in said path in interv'ening relation to corona discharge wire means.

7. A' corona discharge device comprising an elongated dielectric body frame having spaced apart longitudinal coextensive wall flanges presenting respective edges connected by spacer guide rib strips secured at their respective opposite ends to said wall flanges adjacent to said edges and spaced substantially apart longitudinally along said edges,

bridge flanges between and connecting said longitudin'al wall flanges adjacent to opposite ends of the and corona wire means strong on and between said bridge flanges.

. 8. A corona discharge device comprising an elongated dielectric body frame having spaced apart longitudinal coextensive wall flanges presenting respective edges connected by spacer guide rib strips secured at their respective opposite ends to said wall flanges adjacent to said edges and spaced substantially apart longitudinally along said' edges,'

' bridge flanges between and connecting said longitudinal i wall flanges adjacent to opposite ends of the body,

and corona wire means strung on and between said bridge flanges,

said bridge flanges defining therebetween and with said longitudinal'wall flange edges a passage for paper to V be electrostatically charged.

9. A corona discharge device comprising an elongated dielectric body frame having spaced apart longitudinal coextensive wall flanges presenting respective edges connected by spacer guide rib strips secured at their respective opposite ends to said wall flanges adjacent to said edges and spaced substantially apart longitudinally along said edges,

bridge flanges between and connecting said longitudinal wall flanges adjacent to opposite ends of the body, corona wire means strung on and between said bridge flanges,

said bridge flanges defining therebetween and with said longitudinal wall flange edges a passage for paper to be electrostatically charged, and means on said body frame on the opposite side of the bridge flange at each end of the body frame and longitudinally beyond said passage for anchoring the corona discharge wire means.

10. A corona discharge device comprising an elongated dielectric body frame having spaced apart longitudinal coextensive wall flanges presenting respective edges connected by spacer guide rib strips secured at their respective opposite ends to said wall flanges adjacent to said edges and spaced substantially apart longitudinally along said edges,

bridge flanges between and connecting said longitudinal wall flanges adjacent to opposite ends of the body,

corona wire means strung on and between said bridge flanges,

said bridge flanges defining therebetween and with said longitudinal wall flange edges a passage for .paper to be electrostatically charged,

and means on said body frame on the opposite side of the bridge flange at each end of the body frame and longitudinally beyond said passage for anchoring the corona discharge wire means including respective integral anchoring posts and anchoring and clamping means secured to the posts.

11. A corona discharge device comprising an elongated dielectric body frame having spaced apart longitudinal coextensive wall flanges presenting respective edges connected by spacer guide rib strips secured at their respective opposite ends to said wall flanges adjacent to said edges and spaced substantially apart longitud'mally along said edges,

bridge flanges between and connecting said longitudinal wall flanges adjacent to opposite ends of the body, corona wire means strung on and between said bridge flanges,

said bridge flanges defining therebetween and with said longitudinal wall flange edges a passage for paper to be electrostatically charged,

means on said body frame on the opposite side of the bridge flange at each end of the body frame and longitudinally beyond said passage for anchoring the corona discharge wire means including respective integral anchoring posts and anchoring and clamping means secured to the posts,

said body frame being open throughout its length on the side opposite said spacer and guide rib strips, and a metallic cover hood member assembled with said open side and opposing said corona discharge wire means. 12. A corona discharge device comprising an elongated dielectric body frame having spaced apart longitudinal coextensive wall flanges presenting respective edges connected by spacer guide rib strips secured at their respective opposite ends to said wall flanges adjacent to said edges and spaced substantially apart longitudinally along said edges,

bridge flanges between and connecting said longitudinal wall flanges adjacent to opposite ends of the body,

corona wire means strung on and between said bridge flanges,

said bridge flanges defining therebetween and with said longitudinal Wall flange edges a passage for paper to be electrostatically charged,

means on said body frame on the opposite side of the bridge flange at each end of the body frame and longitudinally beyond said passage for anchoring the corona discharge wire means including respective integral anchoring posts and anchoring and clamping means secured to the posts,

said body frame being open throughout its length on the side opposite said spacer and guide rib strips,

a metallic cover hood member assembled ,with said open side and opposing said corona discharge wire means,

and means on said posts and said cover hood member for orienting and retaining the cover hood in assembly.

13. A corona discharge device comprising an elongated hollow dielectric plastic body having opposed spaced longitudinal walls including longitudinal edges and con nected together adjacent to their opposite ends by corona discharge wire-supporting bridge flange means,

corona discharge wire means strung onto and between said bridge flange means longitudinally between said longitudinal walls,

a series of integral paper guide and spacer rib elements connected to and between said edges at spaced intervals therealong,

said walls defining a longitudinal opening from said body frame on the opposite side from said ribs,

and a metallic channel hood cover closing said opening and having spaced apart longitudinal flanges complementally engaging within the respective side walls adjacent to said opening and opposing said corona wire means in spaced relation.

14. A corona discharge device comprising:

an elongated hood structure to extend across the path of movement of paper to be charged,

corona discharge wire means supported longitudinally in the hood structure,

said hood structure affording an essentially non-conductive area longitudinally back of said wire means, and conductive area means longitudinally alongside said non-conductive area.

15. A corona discharge device comprising an elongated hollow dielectric plastic body frame having longitudinal walls and end walls connecting the same,

integral reinforcing bridge flanges adjacent to but spaced from the respective end walls,

said bridge flanges having aligned notches therein,

and a corona discharge Wire strung between said flanges and engaging in said notches.

16. A corona discharge device comprising an elongated hollow dielectric plastic body frame having longitudinal walls and end walls connecting the same,

integral reinforcing bridge flanges adjacent to but spaced from the respective end walls,

said bridge flanges having aligned notches therein,

a corona discharge wire strung between said flanges and engaging in said notches, said notches comprising a pair of notches in each of the flanges,

said corona wire comprising a loop engaged on one of the flanges between the notches and having the opposite end portions of the wire extending through the notches in the remaining flange,

and means securing said end portions of the wire to the body frame.

17. A corona discharge device comprising an elongated hollow dielectric plastic body frame having longitudinal walls and end walls connecting the same,

integral reinforcing bridge flanges adjacent to but spaced from the respective end walls,

said bridge flanges having aligned notches therein,

a corona discharge wire strung between said flanges and engaging in said notches,

said notches comprising a pair of notches in each of the flanges,

said corona wire comprising a loop engaged on one of the flanges between the notches and having the opposite end portions of the wire extending through the notches in the remaining flange,

means securing said end portions of the wire to the body frame,

and means comprising a tensioning spring engaging said loop of the wire adjacent to said portion between said notches of said one flange.

18. A corona discharge device comprising an elongated hollow dielectric plastic body frame having longitudinal walls and end walls connecting the same,

integral reinforcing bridge flanges adjacent to but spaced from the respective end walls,

said bridge flanges having aligned notches therein,

a corona discharge wire strung between said flanges and engaging in said notches,

said notches comprising a pair of notches in each of the flanges,

said corona wire comprising a loop engaged on one of the flanges between the notches and having the opposite end portions of the wire extending through the notches in the remaining flange,

means securing said end portions of the wire to the body frame,

means comprising a tensioning spring engaging said loop of the wire adjacent to said portion between said notches of said one flange,

and means connected to said spring for connecting the corona wire to a source of potential.

19. In a corona discharge device,

a pair of dielectric hollow frame bodies,

corona discharge wires supported by said bodies,

means separably connecting said bodies in abutting coextensive relation,

said bodies defining therebetween a passage for paper to receive electrostatic charge,

and integral dielectric spacer and guide means on said bodies between said corona discharge wires and in part defining said passage.

20. In a corona discharge device,

a self-sustaining thin plastic hollow body comprising spaced parallel longitudinal walls defining a longitudinal opening entirely along the edges on one side thereof and a partial opening along the edges on the opposite side thereof with end walls connecting the longitudinal walls and reinforcing and corona discharge wire supporting bridge flange means connecting said longitudinal walls along said one side adjacent to but spaced from said end walls,

and a metallic cover member engaged on the body within said longitudinal walls and alongsaid first mentioned edges and stiffening the body against transverse bending through said longitudinal walls.

References Cited by the Examiner UNITED STATES PATENTS 2,922,883 1/ 1960 Giaimo 250--49.5 2,965,481 12/1960 Gundl-ach 250-495 3,075,078 1/1963 Olden 250-49.5 3,088,386 5/1963 Sugarman l.7

M. HENSON WOOD, 111., Primary Examiner.

J. N. ERLICH, Assistant Examiner. 

1. A CORONA DISCHARGE DEVICE COMPRISING, OPPOSED DIELECTRIC BODY FRAMES DEFINING A NARROW PASSAGE GAP THEREBETWEEN AFFORDING A PATH FOR PAPER TO BE ELECTROSTATICALLY CHARGED, CORONA DISCHARGE WIRES STRUNG ON SAID BODY FRAMES ACROSS SAID PASSAGE, AND SPACED APART INTEGRAL DIELECTRIC SPACER AND PAPER GUIDE RIBS ON SAID FRAMES INTERPOSED BETWEEN SAID WIRES AND SAID PATH AND EXTENDING GENERALLY DIAGONALLY RELATIVELY TO THE PATH. 